diff options
| author | Cherry Mui <cherryyz@google.com> | 2025-06-22 15:40:02 -0400 |
|---|---|---|
| committer | Cherry Mui <cherryyz@google.com> | 2025-09-26 17:13:31 -0700 |
| commit | 53009b26dd2e8b75fba8b44849e1d323ddb2a31f (patch) | |
| tree | 09416fd14429b1519dbce83fcd79034cd60596c6 /src/runtime/mpagealloc.go | |
| parent | 3a5df9d2b20c0f059c463b5d51e89be17a2c685b (diff) | |
| download | go-53009b26dd2e8b75fba8b44849e1d323ddb2a31f.tar.xz | |
runtime: use a smaller arena size on Wasm
On Wasm, some programs have very small heap. Currently,
we use 4 MB arena size (like all other 32-bit platforms).
For a very small program, it needs to allocate one heap
arena, 4 MB size at a 4 MB aligned address. So we'll
need 8 MB of linear memory, whereas only a smaller
portion is actually used by the program. On Wasm, samll
programs are not uncommon (e.g. WASI plugins), and
users are concerned about the memory usage.
This CL switches to a smaller arena size, as well as a
smaller page allocator chunk size (both are now 512 KB).
So the heap will be grown in 512 KB granularity. For a
helloworld program, it now uses less than 3 MB of
linear memory, instead of 8 MB.
Change-Id: Ibd66c1fa6e794a12c00906cbacc8f2e410f196c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/683296
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Diffstat (limited to 'src/runtime/mpagealloc.go')
| -rw-r--r-- | src/runtime/mpagealloc.go | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/runtime/mpagealloc.go b/src/runtime/mpagealloc.go index 83db005051..a30434a534 100644 --- a/src/runtime/mpagealloc.go +++ b/src/runtime/mpagealloc.go @@ -48,6 +48,7 @@ package runtime import ( + "internal/goarch" "internal/runtime/atomic" "internal/runtime/gc" "unsafe" @@ -55,10 +56,12 @@ import ( const ( // The size of a bitmap chunk, i.e. the amount of bits (that is, pages) to consider - // in the bitmap at once. + // in the bitmap at once. It is 4MB on most platforms, except on Wasm it is 512KB. + // We use a smaller chuck size on Wasm for the same reason as the smaller arena + // size (see heapArenaBytes). pallocChunkPages = 1 << logPallocChunkPages pallocChunkBytes = pallocChunkPages * pageSize - logPallocChunkPages = 9 + logPallocChunkPages = 9*(1-goarch.IsWasm) + 6*goarch.IsWasm logPallocChunkBytes = logPallocChunkPages + gc.PageShift // The number of radix bits for each level. @@ -220,6 +223,7 @@ type pageAlloc struct { // heapAddrBits | L1 Bits | L2 Bits | L2 Entry Size // ------------------------------------------------ // 32 | 0 | 10 | 128 KiB + // 32 (wasm) | 0 | 13 | 128 KiB // 33 (iOS) | 0 | 11 | 256 KiB // 48 | 13 | 13 | 1 MiB // |